Art of extracting rare metals from their ores



Patented Feb. 17, 1925.

UNETED STATES PATENT Fries.

KARL B. THEWS, OF DENVER, COLORADO, ASSIGNOR TO WILLIAM A. J. BELL, OF

' DENVER, COLORADO.

ART OF EXTRACTING RARE METALS FROM THEIR ORES.

No Drawing.

To all whom it may concern:

Be it known that I, KARL B. THEWS, German citizen, and resident ofDenver, in the county of Denver and State of Colorado, have inv ntedcertain new and useful Improvements in the Art of Extracting Rare Metalsfrom Their Ores, of which the following is a specification.

Thisinvention relates to the art of extracting rare metal values such asradium, vanadium and uranium from their containing ores particularlysuch ores as carnotite and is intended to efi'ect a substantialreduction in high costs and difficulties which have heretofore beenencountered in the working of such ores and consequently to renderavailable for commercial working ores or tailings of such low grade thatthey could not be worked profitably under methods previously used.

' Oarnotite ore, which is the principal radium bearing ore nowavailable, is of rare occurrence and is located remote from lines ofcheap transportation. Those deposits now known and worked are found insouthwestern Colorado and eastern Utah and con ore, and then unlessexpensive processes of concentration be used, to sort out or select byhand the richer portions so that about 4 tons of the ore are minedinorder to secure 1 ton of commercially extractible ore. Moreover, largeamounts of metalliferous tailings are thrown away because of their beingof too low grade to rework for their contained values.

The term ore is used herein to broadly designate metalliferous mineralcontaining commercially extractible values whether that material be inits original or raw state as it occurs when taken from the mine orwhether it has been subjected to intermediate processing or treatmentwhich still leaves it with a suflicient metallic content Applicationfiled May 10, 1921. Serial No. 468,359.

worth subjecting it to further extraction processes. It thereforeincludes both raw ore and ore that has been subjected to proc essingeither of a mechanical or chemical nature resulting in the production ofore concentrates, tailings, slimes or the like.

Owing to the great amount of material to be treated and to thetransportation difliculties involved, attempts to satisfactorily solvethe' problem of cheap extraction of values from these ores havelogically tended toward the use of highly concentrated or strong acidsfor extraction purposes but without achieving satisfactory results.

The essence of my present invention is based on the discovery that aspecies of extracting agents, previously unrecognized as available forextraction purposes of which oxalic acid is typical and preferable canbe used advantageously and economically. Furthermore it will act toeifect such a complete solution of the desired values that each and allof said values present may be put into solution at a single step andthen by further treatment, may be separated mechanically.

Heretofore the whole field of organic acids has been disregarded byexperts in this field of metallurgy because of their known' acids suchas hydrochloric acid, nitric acid,

sulfuric acid and the like.

Moreover no one was likely to suspect. that such a relatively weak acidas oxalic acid or others of the organic type possessingv reducingproperties, would exercise any distinctive or selective action ineffecting solution of the radium compounds present in carnotite ores orconcentrates.

Of the various organic acids that are economically available in acommercial sense for effecting such extraction I have found that oxalicacid is among the most'satisfactory reagents for use under presentconditions since it seems to effect a more complete solution of thevalues sought than some of the other organic acids of a reducing naturethat might be used, since with oxalic acid used as hereinafter explaineda substantiallywhile from S0 to 90% of thevanmlium value present iscarried out in this same solution Y which is a high percentage even inthe treatment of vanadium ores for vanadium alone. That is to say, in apractical commercial sense the extraction by direct solution in a singlestage is substantially complete since the vanadlum solution is equal tothe best vanadium recovery processes in commercial use and the radiumuranium extraction is very high.

Because of the relatively small quantities of reagents required in myprocess it is possible to treat ores of lower grade than has been thecase heretofore by other more expensive methods of treatment. Theadditional advantage resides in the fact that oxalic acid and otherreducing acids of organic character lend themselves readily to processesof. recover from the waste liquors by evaporation an crystallization ordistillation.

I believe that I am the first to use an organic acid having a reducingproperty, such as'oxalic acid as a solvent reagent 1n the field ofradium'extraction, but whether the advantage derivedfrom the use of sucha solvent reagent is due to the reducing action per se or to theinducing of a colloidal condition which prevents or impedesprecipitation, or to a direct solvent action I am unable to state and isnot necessary to be determined.

For the purpose of illustration I will now give a concrete example ofthe method of treating a carnotite'ore body of a de that is regarded ascommercially wor able under present conditions, it being understood t atthe precise proportions and the specific in edients are onlyillustrative but not prescriptive.

Treating, let us say, 1 ton of carnotite ore with 1.78% uranium oxide (UO content and about 4% vanadium pentoxide (V 0 I first crush orpulverize the ore to a fineness of about 30 mesh in order to prepare itfor the acid bath.

, I then mix a quantity of oxalic acid and hydrochloric acid and waterso as to provide a li uid bath in the .ratio of'about 2 tons of t eliquid or acid bath for each ton of-comminuted ore to be treated. Thisacid mixture is then heated or brought to a boiling condition by passingsteam through the li uid and the comminuted ore is then added ystirring, and the heating or boiling is continued until substantiallythe entire recoverable values are put into solution.

With an ore of the grade above mentioned the total quantity of oxalicand hydrochloric acidiused would be about 10% of the weight of the ore.In preparing this bath the whole acid constituents ma be oxalic acid orother reducing acids, ut it will probably be found advantageousto useydrochloric acid in .a proportion not ex- .smaller, less acid is -Ofcourse, the addition of an undue excess ceeding the amount of oxalicacid, that is, 50% or less of the acid ingredient may be hydrochloricacid instead of the reducing acid with satisfactory results. Itwill beunderstood that in treating other grades of ore than that abovementioned in which the metallic content difiers from that abovedescribed, there should be a corresponding variation in the amount ofacid ingredient used in the acid solution. Instead of mixing the oxalicacid and the hydrochloric acid in the bath before pouring in thecomminuted ore, the oxalic acid may be put in first, then the ore may beadded and the vhydrochloric acid be added shortly thereafter. a

The use of the hydrochloric acid as part of the acid solvent ispreferred because of its greater cheapness, and with the aid of theoxalic or organic reducing acid it serves the purpose of puttingsubstantially all of the commercially recoverable values into solution.v

The solution containing substantiall all the values that is, radium,vana ium,

uranium and also barium is then mechanically separated from the mass ofgangue and slime by filtration or equivalent means and forms the onlymaterial requiring further treatment for the separation and recovery ofthe different values, and the sand and slime forming tailings or refusemay be discarded since they contain negligible amounts of the values.

This common solution containing all the values is then treated with anysuitable precipitating agent, such as sulfuric acid, to precipitate theradium and barium values whlch, in case of sulfuric acid is used, willbe found in the form of sulfates.

The liquor, from which the radium and barium have been so recipitated,still contains the uranium and vanadium values and is then treated witha suitable recipitatin a cut such as lime, in accor anoe with we I. ownpractice, to form a calciumuranal-vandate which may be separated fromthe liquor by filtration, the liquor being discarded. Any other methodsof separating or. preci itating the various values ma be empgiy atdiscretion.

t is to noted also that the quantity of acid used for the purpose offorming the solution of the values may be decreased with the lower gradeores or tailin since as the values to be put into solution are requiredfor that work.

of acid is to be deprecated as being wasteful and needless.-

While in the specific description of the practice of my process I havereferred to the addition of or nic acid solvent .directly to the dilutore or material to be treated, it will be understood that the processdoes not exclude the more indirect method of adding salts of the organicacids which are capable of being acted upon by an acid used to produceorganic acid in the mixture.

The time periods required for the forming of the complete solution'ofthe values are affected not only by the temperature conditions and bythe proportion of acid solvent used, but are also materially shortenedby mechanical stirring or agitation of the fluid mass of ore as will bereadily appreciated by those skilled in this art.

What I claim as my invention is:

1. The improvement in the art of extracting rare metals from carnotiteore which consists in treating a comminuted and di- KARL B. THEWS.

